EleKit TU-8300 300B tube amp

Elekit TU-8300 or TU-LAB














Elekit TU-8300 or TU-LAB




TU-8300 stereo power amplifier with 300B tubes, the most
popular tube, is designed with many flexibilities. Tube lovers
can use his favourite combination of tubes, output
transformers (OPT), volumes, etc and enjoy this experimental
TU-LAB!
Limited Edition
●Triode connection of pentode also available!
Triode-connected pentode and beam tube have equal qualification
and attraction as300B. In this TU-LAB, 8 pin sockets are
equipped, which enables triode connection of such tubes as KT88
(6550), KT66,EL34(6CA7), 6L6GC, etc, without any modifications to
the amplifier.
●Try different OPT and volumes!
A slide universal bracket, or in other words �magical bracket�
(which enables various kinds of OPTs in various shapes to be
installed) is developed for TU-LAB so that most of commercially-
available OPTs for 300B single amplifier can be used.
● Full of ingenuity for high quality sound, stability, safety, and
energy-saving
[�Constant current circuit, self-bias + fixed bias� method]
Constant current circuit is adopted instead of cathode resistors of self-bias method so that a constant plate current flows no matter what tubes in our assumption are used. (rated currency value can be fine-adjusted).




[Power shut-down circuit for upon over-current]
If over-current occurs in either of the OPTs even for one second, the B power supply is shut down and LED indicator at the troubled side shows that there took place a malfunction.
[FET ripple filer]
FET ripple filter, time-proven in the performance of the reduction of hum noise is adopted for the B power supply.
[All tubes heated by AC]
From a conservation point of view, all tubes are heated by AC power so that the power loss in the rectifying circuit is improved and heating is moderated
【Specifications】
.
● World-wide power transformer
A multi power transformer can be used under 4 different
power voltage environments, such as 100V, 115V, 200V, and 230V
(Select the setting location of the corresponding connector upon
assembly.)
● Tubes：300Bx2, 12AT7x2 (No tubes for replacement included)
● Max. output: 8W+8W (by default, with 300B tubes and 8Ω of load
applied)
● Frequency response(-3dB): 15Hz~40kHz
● Residual noise (IEC filtering): 0.5mV (0.1,V when KT88 installed)
● Input sensitivity: 200mV ●DF：6.3 ●Speaker: 4~16Ω
● Output terminal : Gold-plated, binding post
(bare wires up to Φ5mm can be inserted, and banana plugs can also
be used.)
● Input terminal : Gold-plated RCA jack, single stereo line (at the
back)
● Power input : 3P inlet (IEC320)
● Power voltage : 100V AC 50/60Hz
(115V, 200V, and 230V are also available. Change the soldering
location of the connector for power transformer as shown in the
photo below )
Tools required for assembly】
Soldering iron (15~30W), Solder, Soldering iron stand,
Philips screwdriver (＃2), Diagonal cutter, Long-nose
pliers, Allen wrench ( 1.5mm), Penknife, Scissors




● Power consumption: 80W by standard (70W~95W as ip is fine-
adjustable.)
● Dimension: W400xH213xD250 mm
(Chassis with the punched metal cover, protrusion not included.)
● Weight: 10.8kg (fully assembled, without a power cable)
● ip adjustment range: Approx. 50~80mA (L,R independently adjusted)
● Ham balancer function equipped
● A microcomputer is adopted for TU-LAB, for the first time to our
TU series amplifier (warming-up timer ,
cathode voltage monitoring, automatic shut down of B power supply
upon malfunction)
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Enhancing the Illumination light on the volume knob
1.The knob of the TU-8300 contains a hole in the inner side in which enables the installation of a LED to emit a light on the face of the volume knob.








2. You can use the LED as shown in the picture below
Transparent lens are excessively bright when viewed from the front, therefore, we recommend a dispersed lens. Choose the colour of your choice (yellow, red, green, or white).






Connecting and soldering
LEDs must be connected in the correct way, the diagram may be labeled �a� or �+� for anode and �k� or �-� for cathode (yes, it really is �k�, not �c�, for cathode!). The cathode is the shorter lead and which may contain a slight flat on the body of round LEDs. If you look inside the LED, the cathode is the larger electrode (However, this is not an official identification method).
LEDs can be damaged by heat when soldering, but the risk is minimized if you are careful and slow. No special precautions are needed for soldering most LEDs.


3. Solder as finely as possible to the A-node of the LED. Cover the A-node lead with tube so that there is no short circuit.
A ( anode) K(cathode)


4. Insert a (M2 × 5) or (M2.3 × 5) screw into the small hole located in the back of the knob and insert the LED into the hole next to the screw. Next, tighten the screw so the lead is wound around the cathode of the LED. Finally use a nipper and cut the excess lead. See the picture below for details.






5. Make 2 to 3 loops around the inside of the volume knob as shown in the below picture.









6. Carefully attach the knob to the volume axis and ensuring the axis fits in between all the wiring.






7. Appropriate a suitable length of wiring and solder it to the nearest �8.5V� pin (1kΩ was used here) (as indicated by a yellow arrow in the below picture). The two holes as indicated by the light green coloured arrows are for the illumination of the vacuum tube 12AT7 (see picture 9). A φ3 sized LED is appropriate to be installed here.


8. The tube brightness hole for 12AT7 (indicated by the red arrow) is where I have installed the φ3 sized LED. Both ends of the wire are soldered as shown in the picture below. Solder the one end of the wire connected to the 8.5V as shown in picture 7. The cathode is connected to the grounding pin as shown below






9. The emitting light from the volume knob adds to the overall appearance. (the right side of 12AT7 with LED light)





Translated from
http://www.elekit.co.jp/blog/index.php?s=tu-8300






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